B([O-])([O-])[O-].[Na+].[Na+].[Na+].Cl.[NH2:9][CH2:10][CH2:11][C:12]1[CH:19]=[CH:18][C:16]([OH:17])=[C:14]([OH:15])[CH:13]=1.[OH-].[Na+].[CH2:22]([O:29][C:30](Cl)=[O:31])[C:23]1[CH:28]=[CH:27][CH:26]=[CH:25][CH:24]=1.Cl>O>[C:30]([NH:9][CH2:10][CH2:11][C:12]1[CH:19]=[CH:18][C:16]([OH:17])=[C:14]([OH:15])[CH:13]=1)([O:29][CH2:22][C:23]1[CH:28]=[CH:27][CH:26]=[CH:25][CH:24]=1)=[O:31]38.2 g (100 mmol) of sodium borate and 18.9 g (100 mmol) of dopamine hydrochloride were dissolved in 250 ml of water. To the solution thus obtained, was added a 2 N sodium hydroxide solution under a nitrogen gas stream to adjust the pH value to 9. Then 17.1 g (100 mmol) of benzyloxycarbonyl chloride was added dropwise thereto while stirring at 15° C. for 4 hours. Simultaneously, a 2 N sodium hydroxide solution was added to maintain the pH value of the reaction mixture to 9. After continuing the stirring for 2 hours, the mixture was adjusted to pH 1 to 2 with hydrochloric acid and then extracted with diethyl ether. Next, it was dried over anhydrous magnesium sulfate and the solvent was distilled off. After washing the residue with petroleum ether, the crude crystals thus obtained were recrystallized from ethanol/n-hexane (1 : 1 by volume). Thus 27.6 g (yield: 96.5% of the desired compound (m.p.: 134°- 135 ° C.) was obtained in the form of white crystals.
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